IGF fixes and improvements

I've improved the IGF and some related things and fixed some bugs I found:

### improvements
- remove static variables in IGF and SearchActivity
- replaced static onError-callback in SearchActivity by callback interface
 - also improved crouton displaying: never display 2 croutions if anime and manga loading failed, but one with a adapted message
- improved search intent handling
- onNetworkTaskError-callback for NetworkTask
 - now onNetworkTaskFinished() does not get called if there was an error, these can be handled in onNetworkTaskError()
- renamed HomeSectionsPagerAdapter to SectionsPagerAdapter, it's now used for Home and SearchActivity
- do list updates based on a broadcast
 - now lists are only reloaded if something changed, not always after returning from DetailView

### bug fixes
- fixed infinte calling of getRecords() when there are no more pages on paged lists (like upcoming)
- fixed loading more pages on every device rotation on paged lists
- fixed list filter is not remembered if switching from own list to paged list, scroll down till next page is loaded and switch back to own list again
- fixed search result always reloaded from API after rotation